Along with school closures and limiting cars to driving every other day depending on the last number of their licence plate, a raft of other restrictions will seek to reduce the amount of dust.

Officials said extra subway trains and buses would be added to handle the additional strain on public transport.

Before: The Bird's Nest stadium on a regular day (Image: Reuters)

After: Visitors wearing protective masks take a selfie in front of the National Stadium (Image: Reuters)

Beijing was also shrouded in persistent smog for most of November, when power demand soared due to unusually cold weather.

While pollution in the capital improved slightly in the first 10 months of the year, heavy smog that can be seen from space regularly forces Beijing schools to suspend outdoor activities and can even prompt highway closures because of reduced visibility.

There have previously been stretches of severe smog that lasted more than three straight days. However, those had been forecast to last three days or less, so they did not trigger a red alert.

Pollution: People visiting Tiananmen Square (Image: Getty)

A study led by atmospheric chemist Jos Lelieveld of Germany's Max Planck Institute and published this year in Nature magazine estimated that 1.4 million people die prematurely because of pollution in China each year.

China, the world's biggest carbon emitter, plans to upgrade coal power plants over the next five years to tackle the problem, and says its emissions will peak by around 2030 before starting to decline.

While emissions standards have been tightened and heavy investments made in solar, wind and other renewable energy, China still depends on coal for more than 60 per cent of its power.